Electric Bikes Conversion Kits EMTBS eRoad/Commuting What's New?

AKM thru axle hub

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Raboa

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oldie1982

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Jul 16, 2020
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Suringmax SR85TX. I have this motor and have used it for about 20 miles. I use it in my Cannondale Topstone gravel bike.

it’s built into a 700c wheel.
from the information given to me.
36v 250 watts 260rpm
Reduction ratio is 11.3

What else would you like to know?
 
saneagle

saneagle

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Oct 10, 2010
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oldie1982 said:
Suringmax SR85TX. I have this motor and have used it for about 20 miles. I use it in my Cannondale Topstone gravel bike.

it’s built into a 700c wheel.
from the information given to me.
36v 250 watts 260rpm
Reduction ratio is 11.3

What else would you like to know?
Click to expand...
How does it resist the torque reaction?
 
saneagle

saneagle

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oldie1982 said:
Sorry i have no idea what that means.
Click to expand...
When the motor turns the wheel with force (torque). There has to be an equal force trying to turn the motor in the opposite direction, so you have to anchor it somehow. The more torque the motor gives, the stronger the anchoring needs to be. Normal motors have flats on the axle to which we fit torque arms anchored to the frame or forks. Without torque arms, high torque motors twist themselves out of the drop-outs.
 
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oldie1982

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Jul 16, 2020
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Oh yes got you now.

With the motor in the dropouts without the thru axle in place. If pushing the wheel in the opposite direction to forward, the motor spins in the drop outs on its axle. If you hold the motor axle with a little bit of pressure then it wont spin on its axle. I hope this makes sense.

My thru axle frame has this little nub on either side where the thru axle motor fits. I think most thru axle frames will have this. Photos attached of my actual frame.

The motor fits in such a way in the dropouts that the cable has to point down (like you would a normal hub motor to avoid water ingress). The motor has a semi circular fitting that slots into the drop out and rests on this small nub.

The twisting torque isnt that much to be honest. Compared to my other Bafang Motor 36v SWX02 CST , this has less torque and less power. I can clearly notice the difference.

However if this motor had more torque i dont think those little nubs would last very long.

I hope that gives enough information. Im not sure i explained the above correctly, i can clarify more if you are more specific.
 

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saneagle

saneagle

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oldie1982 said:
Oh yes got you now.

With the motor in the dropouts without the thru axle in place. If pushing the wheel in the opposite direction to forward, the motor spins in the drop outs on its axle. If you hold the motor axle with a little bit of pressure then it wont spin on its axle. I hope this makes sense.

My thru axle frame has this little nub on either side where the thru axle motor fits. I think most thru axle frames will have this. Photos attached of my actual frame.

The motor fits in such a way in the dropouts that the cable has to point down (like you would a normal hub motor to avoid water ingress). The motor has a semi circular fitting that slots into the drop out and rests on this small nub.

The twisting torque isnt that much to be honest. Compared to my other Bafang Motor 36v SWX02 CST , this has less torque and less power. I can clearly notice the difference.

However if this motor had more torque i dont think those little nubs would last very long.

I hope that gives enough information. Im not sure i explained the above correctly, i can clarify more if you are more specific.
Click to expand...
Thanks for that. It doesn't look very secure to me. If I understand right, the torque is resisted by that little bit of aluminium. Is that right? Is there any way you can attach an arm to the motor, like if there are flats on the axle?

A normal hub-motor has flats on the axle that slot into the drop-outs. On their own, they're not enough to resist the torque. There are large flange nuts on the axle. Most of thee torque is resisted by their friction as long as they're really tight. Anybody that doesn't do the nuts tight enough will see there motor spin out. I always recommend at least one torque arm unless the frame or forks are steel.
 
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oldie1982

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Jul 16, 2020
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saneagle said:
Thanks for that. It doesn't look very secure to me. If I understand right, the torque is resisted by that little bit of aluminium. Is that right? Is there any way you can attach an arm to the motor, like if there are flats on the axle?
Click to expand...
That is right, just that little bit of aluminium as far as i can recall. I will when i get a chance, flip the bike over and recheck. Take some photos or videos if i can. I will check if its possible to attach some sort of washer/torque arm.

I also purchased a Boost thru axle motor which came with some type of washers, same semi circular shape as the thru axle. What i dont remember is what they were for. I will dig them out and post some pictures.

saneagle said:
A normal hub-motor has flats on the axle that slot into the drop-outs. On their own, they're not enough to resist the torque. There are large flange nuts on the axle. Most of thee torque is resisted by their friction as long as they're really tight. Anybody that doesn't do the nuts tight enough will see there motor spin out. I always recommend at least one torque arm unless the frame or forks are steel.
Click to expand...
Yes. Agreed.
 
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saneagle

saneagle

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Raboa said:
Topeka do a thru axle trailer adapter, I don't know if this could modified to fit torque arms
Click to expand...
The problem is that a through-axle motor isn't fixed to the axle. The axle goes right through the motor and screws to the frame, which is why I'm puzzled about how the torque is resisted. The stub on the right side is round and concentric, so can't do anything. The stub on the left side has an asymmetric feature on it, but it can't do anything unless there's something that engages with it. Normal through axle hubs have round stubs on both sides, so I can't see why a frame should have any features that could engage with the motor, so that only leaves friction between the stubs and the inside of the frame. I must be missing something.

The Keyde through axle motor has D-shape stubs on both sides, which I guess will locate in a frame if it has D-shape recesses in it.

The Grin one comes with an attached torque arm.
 
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oldie1982

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Jul 16, 2020
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Hopefully this will clarify some bits.

Unfortunately on my Cannondale Topstone it has a little bit of aluminium and then a blank and then some more aluminium for the thru axle to sit in. See the photos. It’s hard to make out but I think the rest of the thru axle slot does offer some support to the thru axle motor. It’s not a tight fit though. Once the thru axle is tightened the motor does not move. In my opinion a more powerful motor with more torque may spin like it would in a normal dropout frame or break the little bit of aluminium that holds it in place.

I don’t think all thru axle frames are like this. For example a replaceable dropout from my mountain bike has a full recess for the thru axle to sit in. This is a lot beefier and will support the thru axle better. Again it’s not a tight fit. See the picture

As mentioned in another post it’s only the left side that offers any support to the thru axle motor. The right side is just round.

Picture also showing how the cable exits the frame. It’s not totally towards the bottom.

I also have a Boost Bikes thru axle motor. Now that has D shaped axles on both ends. The motor also comes with torque washers that take the shape of the thru axle slot on the frame. This gives support to both sides. This is not a normal thru axle motor hence the D shaped axles. The D shaped axles have a smaller hole so you have a QR skewer that holds it in place instead of a long thick bolt like in normal thru axles.
 

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